1. Field of the Invention
The present invention relates to a semiconductor device for driving a liquid crystal panel, and more particularly to a semiconductor device for driving a liquid crystal panel including a self test circuit performing a so-called burn-in test in which a supply voltage is applied to the semiconductor device under high temperature condition.
2. Description of the Related Art
To assure the quality and reliability of semiconductor integrated circuits, it is generally necessary and indispensable to perform an accelerated life test under high temperature normally called burn-in in order to stabilize their characteristics and eliminate early failures, prior to actual use. The burn-in can remove semiconductor integrated circuits having inherent and latent defects, which will suffer faults occurring with passage of time or by applied stresses, because of the variance in manufacture or the like. Recently, various types of acceleration test such as static burn-in, dynamic burn-in and monitored burn-in have been introduced and put into practice with the developments of semiconductor integrated circuits having a number of pins, higher function, and larger scale.
In order to conduct such burn-in, generally, it is necessary to make ready sockets for accommodating semiconductor integrated circuits, a board for mounting those sockets, and an oven, or a pyrostat, for heating the semiconductor integrated circuits in sockets on the board and keeping them under high temperature. A semiconductor device for driving a liquid crystal panel which contains a self-burn-in circuit having functions necessary for the above-mentioned types of burn-in system is known.
FIG. 1 shows an example of such a semiconductor device for driving a liquid crystal panel containing a self burn-in circuit (not shown in FIG. 1). Such a self burn-in circuit may be provided with a pulse generator for imitating an operation of the device under actual use. The semiconductor device 20 is connected with a plurality of power supplies when a burn-in test is performed.
The semiconductor device 20 for driving a liquid crystal panel (not shown in FIG. 1) includes a self-burn-in circuit, a liquid crystal drive output unit 21, terminals 22 and 23 through which given powers are supplied respectively for an ordinary operation and burn-in, and a terminal 24 through which a drive output is supplied to the liquid crystal panel.
Power supplies 31, 32, 33, and 34 necessary to drive liquid crystals for the burn-in test are connected to the terminals 22, and a power supply 35 for logic operations is connected to the terminal 23. The liquid crystal drive power supplies 31, 32, 33, and 34 provide different voltages of V0, V1, V2, V3, and VL, which are applied to the liquid crystal panel drive output unit 21 for a burn-in operation.
In a burn-in test on a semiconductor device for driving a liquid crystal panel, it is generally desirable to conduct the test by the easiest possible method for the purpose of a higher throughput in mass-production.
However, in a conventional semiconductor device for driving a liquid crystal panel as was mentioned above, there has been a problem that many types of power supplies need to be provided and connected, a fact which reduces the mass-production throughput and entails a great cost for the test.